A transmission of a vehicle, which is a transmission device manually operated by a clutch operation of a user or automatically operated by a mission depending on speed, is configured to include a motor.
Generally, an interior permanent magnet (IPM)-type motor having a permanent magnet installed in a rotor is used as a motor of a transmission.
Since an IPM-type motor uses an NdFeB-based permanent magnet which is lightweight and has strong magnetism, it has an advantage of high efficiency and power density.
However, an NdFeB-based permanent magnet includes neodymium (Nd), which is a rare earth, and thus there is a problem of an increase in manufacturing costs of a motor itself due to an increase in price of the rare earth.
Therefore, the recent trend is toward a rare earth-free motor which does not use rare earths.
A rare earth-free motor includes a ferrite magnet motor, an induction motor, a reluctance motor, and so on, and the most representative motor of these is the ferrite magnet motor.
A ferrite magnet motor is a motor using a ferrite magnet, which is a magnetic ceramic, and has an advantage of lower price and easier design than a rare earth motor.
However, since a ferrite magnet is relatively vulnerable to impact, it has problems in that a crack is generated when a motor rotates at a high speed and the performance of the motor is degraded due to discharging a cracked material.